Alarm device



March 19, 1929.

' D. CLARK ALARM DEVICE F l e y 29, 1928 2 Sheets-Sheet 1 IIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIII INVENTOR myaflf/av ATTORNEY Marh 1 9, G. D, CLARK ALARM DEVICE Filed May 29, 1928 1 2 Shaets-Sheet- V INVENTOR aycflfir a I z I I A'TTORNEY Patented Mar. 19, 1929.

UNITED STATES GEORGE D. CLARK, OF SHARPSV-ILL'E,

PENNSYLVANIA, ASSIGNOR TO WESTINGHOUSE ELECTRIC & MANUFACTURING COMPANY, A CORPORATION OF PENNSYLVANIA.

ALARM DEVICE.

Application filed May 29,

The invention relates generally to oil-insulated electrical apparatus and particularly to alarm systems for aiding in the protection of such apparatus upon the development of undesirable conditions therein.

When such undesirable conditions arise in an oil-insulated transformer, they are accompanied, either by an increase in the temperature of the entire transformer windings or by a more violent local increase in temperature,.

which causes gases to be generated in the trouble zone which ascend to the top of the oil. The gases so generated are'often inflammable and there is danger of ignition 16 from a spark in the trouble zone which would produce an explosion within the tank. For this reason, it is desirable to have a protective device actuated upon the occurrence of such trouble, and l have described my invention 20 with particular reference to a bell alarm for such protection. I

The object of my invention, generally stated, is to provide means associated with oil-insulated electrical apparatus for giving an alarm upon the occurrence of undesirable heating conditions which might endanger such apparatus.

A more specific object of my invention is to provide a thermally actuated means for indicating the temperature of a transformer which shall actuate an alarm device upon the occurrence of a predetermined temperature of the transformer windings, or the formation of gases within the transformer tank.

A further object of my invention is to provide a dome which is normally'filled with oil, for the collection of gases generated within an oil-filled electrical apparatus, and a device mounted in the dome which is normally re- 40 sponsive to. the temperature of the oil and to the current in the apparatus, the actuation of which is modified upon the recession of the oil from the dome.

Other objects of my invention will become apparent to those skilled in the art when the following description is considered in condrawings, in

nection w1th the accompanying which;

Figure 1 is a view, in side elevation, of an oil-insulated transformer, the containing tank being in section to show the application of my invention an Fig. 2 is a diagrammatic view of a temperature-indicating and protective system employed in connection with the transformer with oil, and shown in section to illustrate a 1928. Serial No. 281,447.

and tank shown in Fig. 1, in accordance with my invention.

Fig. 3 is a View, in side elevation, of a transformer and a tank therefor partially filled modified form of my invention.

Fig. 4 is a perspective view of the gas-collecting device utilized inthe form of my invention illustrated in Fig. 3.

My invention provides a thermometer or other thermally-responsive element 10 mounted in a dome 11 of a transformer casing 12, the dome being located directly above the transformer windings. The dome 11 and the transformer casing 12 are normally filled with oil 13 in which the thermometer 10 is completely immersed.

The thermometer 10 comprises a bulb 14,

a heating element connected to a current transformer 15, and a dial 16 located outside of the transformer casing 12 to indicate the temperature which influences the thermometer 10 in accordance with the current traversmg the conductor 17 and the cooling effect of the oil 13. k

It is well-known in the art that, when certain troubles occur in the windings of an oilinsulated transformer, gases are generated in the neighborhood of the abnormal condition, and that these gases will ascend to the surface of the oil. The dome 11 may be in the form of a battle disposed beneath the oil, or, in that type of transformer wherein the tank is completely filled with oil. As here illustrated, it may be a part of the transformer tank 12. The dome 11 is provided directly over the transformer windings 18 so that gases, generated by a short-circuit or other disturbance within the windings, will rise into the dome 11 and force the oil 13 downwardly, away from contact with the thermometer bulb 14 and into the vessel 12 through the pipe 12".

When the thermometer bulb 14 is surrounded by gases which have displaced the no oil 13-previously within the dome 11, the cooling effect of the oil upon the thermometer bulb 14 is removed, and the thermometer 10 indicates a higher temperature than it would indicate if immersed in the oil, provided the 5 current traversing the conductor 17 remains the same, since the thermometer bulb 14 is heated in accordance with the current in the transformer 15. For this reason, the thermometer 10 indicates a higher temperature 1 than it would if the oil 13 had not receded from contact with the thermometer bulb 14.

The current transformer 15 is connected to a heating element that is closely associated with the bulb 14 of the thermometer 10, so that the heat imparted to the bulb is substantially proportional to the current traversing the conductor 17, which conductor constitutes the primary of that transformer. Accordingly, the temperature registered on the dial 16 is proportional both to the heat produced by the current delivered by the current transformer 15 and the temperature of the medium surrounding the bulb 14. Obviously, when the bulb 14 is surrounded by the oil 13, the heat generated by the current in the heating element associated with the bulb will be conducted away through circulation of the oil, whereas, when the bulb is surrounded by the gases which have been generated within the windings and which havea thermal capacity much less than that of oil, no such circulation will occur, and the thermometer fluid will ascend to a higher position than it would nor mally attain with. the same current traversing the conductor 17.

The indicating dial 16 is provided with a pair of contact members 19 which, when in engagement, complete the circuit of an alarm device, such as a bell 20. When the indicating arm 21, having one of the contact members 19, is moved to a predetermined high position on the dial 16, thus indicating that a state of abnormal operation exists within the trans former, and that the transformer is endangered by gases accumulating in the dome, or by an excessive current traversing the windings, the alarm circuit is closed and the signal iven. g Obviously, it is possible for suflicient current to traverse the conductor 17 to cause the current transformer 15 to supply suflicient current to heat the bulb to such temperature that the circulation of the oil 13 about the bulb 14; will not prevent the indicating arm 21 of the dial 16 from reaching 7 the predetermined high position at which the protective contacts 19 are brought into engagement, thus giving an alarm. In this case, the transformer is greatly overloaded and action must be taken by the operator or attendant to relieve this abnormal condition. Thus, it is apparent that the protective system may be operated, and the alarm given when dangerous temperatures exist within the transformer, without the existence of gases within the dome 11.

Although the invention has been described with particular reference to a bell alarm 20 as a protective device, it will be readily understood that the operating coil of a circuit breaker might be similarly connected to provide the rotective feature and it is desired that the ell alarm 20 be construed as the equivalent of an protective device which might be actuated when the indicating lever placed from the vicinity 21 of the dial 16 reaches its predetermined high position in which the contact members 9 are in circuit-closing relation.

The protective circuit provided to actuate the bell alarm 20 comprises a battery 22, conductor 23, the contact members 19, conductor 24, the operating coil of the bell 20, and conductor 25. The operation of such a circuit will be readily understood by those skilled in the art and it is, therefore, deemed unnecessary to further describe such operation.

In the embodiment shown in Fig. 3, my invention is adapted for use in a transformer tank which is partially filled with oil. A cone-shaped baflle 26 is suspended from the top of the transformer tank by a rod 27. The vertex or peak of the baffle 26 is situated below the surface of the oil 13 within the tank so. that, during normal operation, the inside of the baflle 26 is completely filled with oil.

The thermometer 10 is mounted near the vertex of the cone 26 and operates in a manner exactly as described hereinbefore.

With the bafile 26 disposed as shown in Fig. 3, directly above the coils 18, gases which are generated in the coils 18, upon the occurrence of trouble or during abnormal operation, will be caught by the baflle and directed to its vertex to force the oil within the baflle downwardly until the thermometer 10 is finally surrounded by gases and may operate as described above when situated in the dome 11 of the transformer tank shown in Fig. 1.

The baffle 26 provides a pocket for the collection of gases generated within the trans- 100 former windings so that m invention may be readily adapted to transformers which are partially filled with oil.

Since it will be possible to modify the embodiment set forth and adapt it to numerous 105 applications without departing from the spirit and scope of my invention, it is desired that the foregoing description shall be construed as merely illustrative and not in a limiting sense.

I claim as my invention:

1. In a fluid-insulated electrical apparatus, a casing surrounding the device and containing the fluid, said casing being provided with a dome normally filled with said fluid, a ther- 115 mally responsive element mounted in the dome and normally surrounded by the fluid, means for heating the thermally-responsive element in accordance with the current traversing the apparatus, said fluid being dis- 1 of the thermallyresponsive element upon the formation of gases incident to trouble within the apparatus, whereby the cooling effect of the fluid is removed from the thermally-responsive ele- 1 ment.

2. In an oil-insulated electrical apparatus,

a casing surrounding the apparatus and confining the oil, said casing being provided with a dome normally filled with sand oil, a ther- 130 paratus comprising mally-responsive element mounted in the dome and normally surrounded by the oil, said thermally-responsive element being influenced by the current traversing the apparatus and the temperature of the oil, said thermally-responsive element being disposed to actuate an alarm upon the recession of the surrounding oil.

3. In an oil-insulated electrical apparatus, a casing surrounding the apparatus and confining the oil, said apparatus being provided with a dome normally filled with said oil, means for giving an alarm upon the occur rence of abnormal conditions within the ap a thermally-responsive element, mounted in the dome, surrounded by the oil and heated by the currenttraversing the apparatus, whcreby, during such abnormal operation of the apparatus as is accompanied by-the production of gases, the gases collect in the dome to displace the oil and permit the thermal element to become heated to a high temperature and actuate mechanism for giving the alarm.

4. In an oil-insulated electrical apparatus, a casing surrounding the apparatus and confining the oil, said apparatus being provided with a dome normally filled with said oil, means for protecting the apparatus upon the occurrence of abnormal conditions within the device comprising a thermally responsive element, mounted in the dome, surrounded by the oil and heated by the current traversing the apparatus, whereby, during certain abnormal operations of the apparatus, gases collect in the dome and displace the oil, thus permitting the thermal element to become heated to a high temperature, and a. protective circuit completed by the thermal element when so heated.

5. In a temperature-indicating device for oil-filled transformers, protective means for the transformer, a thermometer bulb heated in accordance with the current traversing the transformer and normally cooled by surrounding oil, means for displacing said oil from the vicinity of the thermometer bulb upon the occurrence of trouble within the transformer, thereby causing the thermometer to actuate the protective means.

6. In an oil-insulated transformer in which gases are generated during abnormal operation, a pocket for collecting said gases, said pocket being normally filled with oil, a protective circuit, a thermally-responsive element mounted in the pocket and disposed to complete the protective circuit upon a predetermined heating of the transformers, or v upon the displacement of oil from the pocket while current is traversing the transformer.

In testimony whereof, I have hereunto subscribed my, name this 25th day of May, 1928.

GEORGE D. CLARK. 

